Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Preferred stock	Common stock	Other paid-in capital	Retained earnings	Accumulated other comprehensive loss	Treasury stock
Balance (in shares)		150,000
Balance (in shares)			195,843,297
Treasury stock (in shares)							(538,921)
Balance (in shares)		0
Balance (in shares)	195,843,297		195,843,297
Treasury stock (in shares)	(538,921)						(538,921)
Balance at Dec. 31, 2016	$ 2,316,244	$ 15,000	$ 195,843	$ 1,232,478	$ 912,282	$ (35,733)	$ (3,626)
Net income	78,539				78,539
Other comprehensive income	(56)					(56)
Dividends declared on preferred stocks	(171)				(171)
Dividends declared on common stock	(75,192)				(75,192)
Stock-based compensation	1,629			1,855	(226)
Repurchase of common stock							(64,384)
Repurchase of common stock	(1,684)						$ (1,684)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings				(2,441)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)							64,384
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings							$ 1,684
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(757)
Redemption of preferred stock (shares)		(150,000)
Redemption of preferred stock		$ (15,000)
Redemption of preferred stock	(600)				(600)
Redemption of preferred stock	$ (15,600)
Balance (in shares) at Jun. 30, 2017		0
Balance (in shares) at Jun. 30, 2017	195,843,297		195,843,297
Treasury stock (in shares) at Jun. 30, 2017	538,921						538,921
Balance at Jun. 30, 2017	$ 2,302,952	$ 0	$ 195,843	1,231,892	914,632	(35,789)	$ (3,626)
Balance (in shares)		0
Balance (in shares)	195,843,297		195,843,297
Treasury stock (in shares)	(538,921)						(538,921)
Balance at Mar. 31, 2017						(36,185)
Net income	$ 41,215
Other comprehensive income	396					396
Redemption of preferred stock	$ (600)
Balance (in shares) at Jun. 30, 2017		0
Balance (in shares) at Jun. 30, 2017	195,843,297		195,843,297
Treasury stock (in shares) at Jun. 30, 2017	538,921						538,921
Balance at Jun. 30, 2017	$ 2,302,952	$ 0	$ 195,843	1,231,892	914,632	(35,789)	$ (3,626)
Balance (in shares)		0
Balance (in shares)	195,843,297		195,843,297
Treasury stock (in shares)	(538,921)						(538,921)
Balance (in shares)	195,843,297		195,843,297
Treasury stock (in shares)	(538,921)						(538,921)
Cumulative effect of adoption of ASU 2014-09 | Accounting Standards Update 2014-09	$ (970)				(970)
Adjusted balance at January 1, 2018	$ 2,428,073		$ 195,843	1,233,412	1,039,778	(37,334)	$ (3,626)
Balance (in shares)	196,557,245		196,557,245
Treasury stock (in shares)	(538,921)						(538,921)
Balance at Dec. 31, 2017	$ 2,429,043		$ 195,843	1,233,412	1,040,748	(37,334)	$ (3,626)
Net income	86,239				86,239
Other comprehensive income	1,158					1,158
Reclassification of certain prior period tax effects from accumulated other comprehensive loss | Adjustments for new accounting pronouncement	0				7,959	(7,959)
Dividends declared on common stock	(77,286)				(77,286)
Stock-based compensation	2,251			2,517	(266)
Repurchase of common stock							(182,424)
Repurchase of common stock	(5,020)						$ (5,020)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings				(7,350)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)							182,424
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings							$ 5,020
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(2,330)
Issuance of common stock (shares)			713,948
Issuance of common stock	17,993		$ 714	17,279
Redemption of preferred stock	0
Redemption of preferred stock	$ 0
Balance (in shares) at Jun. 30, 2018	196,557,245		196,557,245
Treasury stock (in shares) at Jun. 30, 2018	538,921						538,921
Balance at Jun. 30, 2018	$ 2,451,078		$ 196,557	1,245,858	1,056,424	(44,135)	$ (3,626)
Balance (in shares)	196,557,245		196,557,245
Treasury stock (in shares)	(538,921)						(538,921)
Balance at Mar. 31, 2018						(44,860)
Net income	$ 43,802
Other comprehensive income	725					725
Redemption of preferred stock	$ 0
Balance (in shares) at Jun. 30, 2018	196,557,245		196,557,245
Treasury stock (in shares) at Jun. 30, 2018	538,921						538,921
Balance at Jun. 30, 2018	$ 2,451,078		$ 196,557	$ 1,245,858	$ 1,056,424	$ (44,135)	$ (3,626)
Balance (in shares)	196,557,245		196,557,245
Treasury stock (in shares)	(538,921)						(538,921)